In recent years, many electronic appliances, both consumer and professional, have been automated. This means that many functions that are controlled by the use can also be controlled by an internal program of the appliance. In older non-automated appliances, rotary potentiometers were used to control many functions. Automation of a unit requires the use of knobs or buttons that allow an automated change of parameters and would also work as manual controls. Traditional potentiometers usually cannot be used because they can be set only by an operator. Users are accustomed to a traditional form of a knob as a control device. By turning the knob, a user can increase or decrease the setting of a parameter. An automated control device should work in a similar way. There are several solutions presently being used, all of which have various disadvantages.
One automated design is an array of "up and down" push-buttons. The basic disadvantage of the present automated solutions is the inability to indicate the current position of the control as is possible with traditional potentiometers. In traditional potentiometers, the actual position of the knob is shown by a marker. This allows the user to determine how the control is set. Nothing similar is possible with push-buttons, unless an additional display is provided.
Another example of an automated control is a motorized potentiometer. A motorized potentiometer has the disadvantage that a driving motor is mechanically coupled with the potentiometer shaft. Therefore, there are two factors determining knob position, namely, the user and the motor. This complicates the additional circuitry and makes the whole product very unreliable and expensive.
A third known design of automated control is a rotary multipositional switch with no mechanical stop, surrounded by light emitting diodes (LED) With this control, the user turns the switch and the position of the switch is shown by one of the LEDs, which is activated by associated electronics. This construction has the disadvantages of high cost and inconvenient and unclear reading.